A variety of optical connectors are used in the optical communications industry to mechanically and optically couple an end of an optical fiber cable to an optical fiber receptacle. In general, an optical connector includes a connector housing that is mechanically coupled to at least one optical fiber. The connector housing includes a ferrule that receives and surrounds a portion of the optical fiber adjacent an end of the optical fiber. The optical fiber comprises a fiber core, a cladding that surrounds the core, and a jacket that surrounds the cladding.
FIGS. 1A and 1B illustrate side views of a known optical connector 2 coupled with an optical fiber 3. The optical connector 2 includes a connector housing 4 and a ferrule 5. A portion of the optical fiber 3 is held within the optical connector 2. The optical fiber 3 has a core 3a and a jacket 3b that surrounds the core 3a. For ease of illustration, the cladding is not shown in FIGS. 1A and 1B. In FIGS. 1A and 1B, reference numeral 3a represents the core and the cladding. An end portion of the optical fiber 3 is disposed within the ferrule 5 such that an end 3c of the fiber 3 is flush with an end 5a of the ferrule 5. The end 3c of the fiber 3 is made flush with the end 5a of the ferrule 5 via a polishing process or similar processes. Clamps 6 are used to clamp down on the fiber 3 to hold it in position within the connector housing 4.
One of the problems with optical connectors of the type shown in FIG. 1A occurs at the end 3c of the fiber 3, as will now be described with reference to FIG. 1B. After the optical fiber 3 has been cut and installed in the connector housing 4 as shown in FIG. 1A, temperature and humidity conditions cause the core 3a to shrink and retract away from the end 5a of the ferrule 5 leaving a gap 7 between the end 3c of the core 3a and the end 5a of the ferrule 5. The jacket 3b does not shrink to the same extent as the core 3a due to differences in surface tension, intrinsic tension, and in the coefficients of thermal expansion of the core 3a and the jacket 3b. Because of the gap 7, light passing out of the end 3c of the core 3a reflects off of the jacket 3b, thereby resulting in optical losses. This is sometimes referred to in the optical communications industry as “the pistoning effect.”
One technique that is sometimes used to avoid the pistoning effect involves the use of a special optical fiber that is designed to prevent pistoning from occurring. The optical fiber that is developed for this purpose has a second, outer jacket (not shown) that surrounds the jacket 3b. The jacket 3b becomes a first, inner jacket that is secured to the core 3a (e.g., by an adhesive material) to prevent the core 3a from “pistoning” relative to the jacket 3b. The second, outer jacket is only loosely connected to the first, inner jacket 3b. With this design, pistoning of the core 3a within the first, inner jacket 3b is prevented. Other techniques that involve glue or welding have also been used to prevent the pistoning effect.
Developing a special optical fiber that prevents pistoning from occurring is relatively costly and increases the overall cost of the optical link. Currently, if a special optical fiber is not used, then the optical link must be designed with sufficient margin to overcome the optical losses that occur due to the pistoning effect, which also increases the overall cost of the optical link.